Surfacing machines, such as wood planers and jointers, etc., often make use of at least one powered, rotatable cutter head. The cutter head is typically supplied with a number of axial knives presenting sharpened edges along the outward periphery of the cutter head for removing material passed over the rotating head on a workpiece support surface. In wood planers, often two such cutter heads are used to simultaneously perform surfacing operations on opposing surfaces of the wooden workpiece.
The process involved in mounting the cutter knives to rotatable cutter heads is rather complicated and time consuming. It is therefore desirable to periodically recondition or "joint" the knives on the cutter head rather than removing the knives and sharpening each separately.
Proper equipment used in the jointing operation and correct selection of jointing stones are major assets in accomplishing a proper jointing operation.
A skilled worker may have adequate training and expertise to accomplish a quality job, but may well be frustrated in doing so because of equipment shortcomings. For example, a soft jointing stone is almost always preferred over a hard, dense stone. But the soft stones cannot be used due to the pounding action of the rotating knives against the stone if the stone support "flutters." This is a typical situation with most, if not all, present "dovetail" jointer stone support assemblies. A worn or loose fit in the stone support allows the stone support to jum or "flutter" as the knives rotate into engagement with the stone. Soft stones are easily broken in this situation so the less desirable hard stones must be selected.
Another result of stone support flutter is that an undesirable high or outwardly projecting "heel" is created behind the cutting edge of the knives. This "head" does not assist the knives in the cutting or scraping operation, but instead rubs over the surface of the work piece, often causing burns or, at best, a rough textured surface. Nonetheless, the worker must select a hard stone for the jointing process since a soft stone would be surely broken by the fluttering action of the support and contact with the surfacer knives.
A tight or securely mounted stone holder will facilitate the use of softer stones which remove many times more material in a shorter time. However, the presently available jointer devices cannot be effectively "tightened" to provide firm support for the stone without sacrificing freedom of movement for the stone across the cutter head during the jointing oepration. Dovetail stone mounts will not slide freely when secured in a manner sufficient to reduce or eliminate stone flutter. Older, worn jointing devices simply cannot be adjusted tight enough to accomplish the task, even with the inherent sacrifice of mobility of the stone across the cutter head.
The above problems have been recognized to limit degree by the below-referenced United States patents. However, it is not believed that any of the known references show or suggest the solution embodied in the present invention as set forth below.
U.S. Pat. No. 4,495,734 granted to Rauch in 1985 discloses a grinding arrangement for chopping cutters. The grinding arrangement makes use of a tool mounting bar and guide slidably engaged thereon for supporting the grinding stone. A wheel actuator arrangement is provided for driving and guiding the stone to and fro along the axial length of the cutter head. This arrangement, while making use of wheels in the drive arrangement, still makes use of a singular bar and guide way arrangement for mounting the grinder.
U.S. Pat. No. 3,374,699 to Schmermund discloses a sharpening arrangement for mounting cutter heads and for sharpening the cutter heads. The apparatus includes a support frame for receiving and mounting the cutter head for rotation on an axis that is skewed in relation to a grinding tool support. The grinding tool is movably supported on a pair of guide rods for motion along the cutter head. A stone support is mounted on the rod-mounted carriage by a dovetail arrangement to facilitate radial adjustment of the stone against the cutter head to be sharpened.
The rods and bearings mounting the carriage and stone in the Schmermund device may function to eliminate some of the problems present in a standard dovetail guide arrangement but many of these advantages may be offset by use of the dovetail stone support arrangement. It may therefore be concluded that Schmermund, while providing adequate longitudinal support for the jointing stone, teaches away from the solution presently disclosed in this application by using a dovetail stone mounting arrangement for radial adjustment relative to the blade or cutter head to be sharpened.
U.S. Pat. No. 2,476,177 to Bloom et al issued July 12, 1949, discloses a forage harvester knife sharpener. This device again makes use of an elongated bar mounting a stone holder for adjustment toward or away from the cutters on a drum. The entire mechanism is pivotal about a shaft that extends across the width of the harvester cutting head.
U.S. Pat. No. 933,398 to Osborne granted May 30, 1911, discloses a grinder to planer knives also making use of a bar slidably mounting a jointing stone support.
U.S. Pat. No. 267,579 to M. W. Palmer granted Nov. 14, 1882, discloses a planer knife grinder in which a grinding disc is mounted for rotation with an end-supported shaft adjacent a planar knife head. The powered grinding disc can be moved along the length of the rotable signel shaft by an elongated actuator extending to one side of the planer. The Palmer device is intended to sharpen each knife separately and cannot be used effectively with the planer in operation. A somewhat similar apparatus is disclosed in U.S. Pat. No. 2,620,606 to Dvorak, issued Dec. 9, 1952. Dvorak discloses a sharpening attachment for surfaces in which a grinding wheel is mounted by a pivoted frame to a shaft for sliding movement along the cutter head. The cutter head cannot be operated during the sharpening operation.
Of the above references, none are believed to show or suggest a solution to the problem of securing a jointing stone while enabling relatively free precision motion of the stone in relation to a rotating cutter head as described and claimed below.